Durability design of tunnels: present and future

A service life of 100, 120, or even more years, is required to major infrastructures, such as tunnels, to guarantee that the investment is used in an efficient and rational way. This paper discusses, in relation to the different tunnel excavation methods, the main degradation phenomena affecting the durability of the inner and outer lining concrete and the mitigation strategies, as the choice of the correct cement type, to ensure the durability requirement. The prescriptive approach for durability design, mainly used nowadays, is explained and compared to the performance-based approaches, most advisable for the future, that include test methods to measure durability-related parameters of a concrete mix, that allow to predict its long-term behaviour in the specific exposure conditions.